What causes male sub-fertility?
There are the following common causes:
- Genito-urinary infections e.g. Chlamydia, mycoplasma and several other related infections
- Undescended or delayed descent of testes
- Low or no sperm in the ejaculate after vasectomy and reversal of vasectomy
- Genetic causes (some may be hereditary)
- Diseases requiring removal of the testis e.g. cancers
- Diseases requiring chemotherapy or radiotherapy
- Hypothalamic and pituitary disorders
Systemic diseases such as cystic fibrosis, thalassaemia and many others
Genetic or hereditary male sub-fertility:
The incidence of chromosomal abnormalities is approximately 13.7% in men with no sperm in the ejaculate and 4.6% in men with low sperm counts. The incidence in men with normal sperm counts is 0.5%. This information is not relevant to the offspring if they have been conceived with donated sperm.
Normal chromosome pattern:
This for every man is 46XY. There are 22 pairs of normal chromosomes (total 44) called the `autosomes’ and these are responsible for the general characteristics and bodily functions. The 23rd pair are the sex chromosome and in men this is expressed as XY, where X codes for female development and Y codes for development as a male. Females have two X-chromosomes and hence an XX pattern. In males the Y chromosome is the dominant one and this dictates development of the baby as a male.
- In the majority of men, there is no abnormality of chromosome numbers i.e. the total numbers are normal as 46XY, but a structural aberration of the sex chromosome exists with either missing or modified genetic information on the Y chromosome. This chromosome is responsible for testicular development and sperm formation. In the event of loss of genetic material or its modification, men may have genetically determined low sperm counts and sub-fertility. We do not yet know all forms of gene deletions or mutations although active research is bringing more new information forward at a considerable pace.
- In couples undergoing ICSI treatment with their own sperm, the same Y chromosome will be passed on to the sons and there may be a risk of passing the defect to the male child whose future fertility may be affected. This problem would not occur if donor sperm is used.
- In some men, there is an extra sex chromosome giving a pattern of 47XXY or 47XYY. The ICSI success rate in this case is also very low and variable. This problem would also not occur if donor sperm is used.
- If there is an abnormality with the main 22 pairs of chromosomes, then the success rates after ICSI are also lower, there is an increased risk of miscarriage and, in ongoing pregnancies there will be a risk of congenital abnormality and/or mental retardation. This problem too would be bypassed if donor sperm is used.